Abstract
Antibiotic resistance concerns various areas with high consumption of antibiotics, including husbandry. Resistant strains are transmitted to humans from livestock and agricultural products via the food chain and may pose a health risk. The commensal microbiota protects against the invasion of environmental strains by secretion of bacteriocins, among other mechanisms. The present study aims to characterize the bactericidal potential of bacteriocinogenic Escherichia coli from healthy humans against multidrug-resistant and antibiotic-sensitive strains from pigs and cattle. Bacteriocin production was tested by the double-layer plate method, and bacteriocin genes were identified by the PCR method. At least one bacteriocinogenic E. coli was detected in the fecal samples of 55% of tested individuals, adults and children. Among all isolates (n = 210), 37.1% were bacteriocinogenic and contained genes of colicin (Col) Ib, ColE1, microcin (Mcc) H47, ColIa, ColM, MccV, ColK, ColB, and single ColE2 and ColE7. Twenty-five E. coli carrying various sets of bacteriocin genes were further characterized and tested for their activity against zoonotic strains (n = 60). Strains with ColE7 (88%), ColE1-ColIa-ColK-MccH47 (85%), MccH47-MccV (85%), ColE1-ColIa-ColM (82%), ColE1 (75%), ColM (67%), and ColK (65%) were most active against zoonotic strains. Statistically significant differences in activity toward antibiotic-resistant strains were shown by commensal E. coli carrying MccV, ColK-MccV, and ColIb-ColK. The study demonstrates that bacteriocinogenic commensal E. coli exerts antagonistic activity against zoonotic strains and may constitute a defense line against multidrug-resistant strains.
Highlights
The intestinal microbiota is a highly diverse and dynamic community
The aim of this study is to investigate the bactericidal potential of commensal, bacteriocinogenic
The presence of one bacteriocin gene was detected in 32 strains, while co-occurrence of two or more colicin genes was found in 37 strains
Summary
The intestinal microbiota is a highly diverse and dynamic community. It consists of indigenous flora and autochthonous microorganisms from the environment, which compete for niches and nutrients to colonize the intestinal habitat [1,2]. Protection of commensal species against invasion by exogenous microorganisms is a part of colonization resistance and involves the production of inhibitory molecules such as bacteriocins [3,4]. Their operons, under the LexA promoter, include one to three genes responsible for the unique action of the system-toxin, immunity, and lysis. Colicin production is induced in stressful conditions that stimulate SOS responses or by nutrient depletion, but small amounts
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